Thin film silicon wafer and method for manufacturing the same

ABSTRACT

Provided are a thin film silicon wafer having high gettering capability, a manufacturing method therefor, a multi-layered silicon wafer formed by laminating the thin film silicon wafers, and a manufacturing method therefor. The thin film silicon wafer is manufactured by: forming one or more gettering layers immediately below a device layer which is formed in a vicinity of a front surface of a semiconductor silicon wafer; fabricating a device in the device layer of the semiconductor silicon wafer; and after the device has been fabricated, removing part of the semiconductor silicon wafer from a rear surface thereof to immediately below the gettering layers so as to leave at least one of the gettering layers in place. As a result, the thin film silicon wafer is allowed to have gettering capability even after having been reduced in thickness to be in a thin film form.

TECHNICAL FIELD

The present invention relates to a gettering method, which is atechnology of removing heavy metal impurities that have an adverseeffect on device operations in a semiconductor silicon singlecrystalline substrate, and to a thin film silicon wafer having highgettering capability, a manufacturing method therefor, a multi-layeredsilicon wafer formed by laminating the thin film silicon wafers, and amanufacturing method therefor.

BACKGROUND ART

Along with higher densification and higher integration of devicesincluding semiconductor integrated circuits, there is a rapidlyincreasing demand for stabilization of device operations. In particular,improvement in characteristic values with regard to leakage current,oxide dielectric breakdown strength, and the like is an importantproblem.

However, even now, the fear of contamination by such undesirable heavymetals as impurities of Cu, Fe, Ni, and the like remains undenied inmanufacturing steps for the semiconductor integrated circuit. It iswidely known that those heavy metal impurities which exist as a solidsolution state in a silicon single crystal significantly deteriorate theabove-mentioned characteristics of leakage current and oxide dielectricbreakdown strength.

Accordingly, various gettering technologies have been developed as a wayto remove those heavy metal impurities out of a device operating region.There are known, for example, an internal gettering (IG) method whereinoxygen atoms contained in a silicon single crystal that has beenmanufactured through a CZ method are precipitated as oxygen precipitatesto capture heavy metals within strains around the precipitates, a methodwherein elements of some kind are ion-implanted into a vicinity ofdevice layers to generate intentionally strains or defect layers andheavy metals are gettered into the strains or defect layers, and amethod wherein a polycrystalline silicon film is formed on a rearsurface of a silicon wafer so as to capture heavy metal impurities withstrains generated in polycrystalline grain boundaries.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, in a recent device structure such as a multi-chip device inwhich high integration is achieved by reducing a device formation layerin thickness to make a thin film and laminating and depositing a numberof the thin films, even if a gettering layer has been formed in advancein the interior of a silicon wafer or on a rear surface thereof, thegettering layer is peeled off at a stage of making the thin film, whichcauses gettering capability thereof to be lost after the multi-layeredstructure has been formed. Even if gettering capability is imparted to alowermost layer position of the multi-layered wafer, it is necessarythat impurities in a vicinity of a front surface layer of themulti-layered wafer permeate through a plurality of device layers inorder to be gettered to a rear surface layer thereof.

The present invention has been made in view of the problems, and has anobject of providing a thin film silicon wafer having high getteringcapability, a manufacturing method therefor, a multi-layered siliconwafer formed by laminating the thin film silicon wafers, and amanufacturing method therefor, based on knowledge that, in a siliconwafer having a multi-layered structure in which device layers of thinfilms are laminated, there is effective a structure in which getteringcapability is imparted to each of the device layers, and there is alsoeffective a method in which a plurality of layers each having getteringcapability (hereinafter simply referred to as gettering layers) areimparted to each of the thin film silicon wafers, and unnecessaryimpurities are collected together in the gettering layers before makingthe thin films from the device layer so that the impurities captured inthe gettering layers are removed together the layers when making thethin films, because the method is capable of reducing the fear thatrecontamination may occur at a later stage. The present invention alsohas an object of providing a thin film silicon wafer, a manufacturingmethod therefor, a multi-layered silicon wafer formed by laminating thethin film silicon wafers, and a manufacturing method therefor, which arecapable of providing gettering capability even against elements causingcontamination after the thin film silicon wafers have been deposited toform the multi-layered structure by leaving at least one of a pluralityof formed gettering layers in place.

Means for Solving the Problems

A thin film silicon wafer according to the present invention hasgettering capability even after having been reduced in thickness to bein a thin film form, the thin film silicon wafer being manufactured by:forming one or more gettering layers immediately below a device layerwhich is formed in a vicinity of a front surface of a semiconductorsilicon wafer; fabricating a device in the device layer of thesemiconductor silicon wafer; and after the device has been fabricated,removing part of the semiconductor silicon wafer from a rear surface ofthe semiconductor silicon wafer to immediately below the getteringlayers so as to leave at least one of the gettering layers in place.

A manufacturing method for a thin film silicon wafer which has getteringcapability even after having been reduced in thickness to be in a thinfilm form according to the present invention includes the steps of:forming one or more gettering layers immediately below a device layerwhich is formed in a vicinity of a front surface of a semiconductorsilicon wafer; fabricating a device in the device layer of thesemiconductor silicon wafer; and after the device has been fabricated,removing part of the semiconductor silicon wafer from a rear surface ofthe semiconductor silicon wafer to immediately below the getteringlayers so as to leave at least one of the gettering layers in place.

A multi-layered silicon wafer structure according to the presentinvention has a structure in which: a plurality of the thin film siliconwafers according to the present invention are laminated in layers; eachof the laminated layers includes an individual device; and getteringlayers are provided immediately below all of the layers including theindividual devices.

A manufacturing method for a multi-layered silicon wafer structureaccording to the present invention includes the step of laminating inlayers a plurality of the thin film silicon wafers according to thepresent invention, to thereby manufacture the multi-layered siliconwafer structure in which each of the laminated layers includes anindividual device, and gettering layers are provided immediately belowall of the layers including the individual devices.

A multi-layered silicon wafer according to the present invention ismanufactured by laminating a plurality of thin film silicon wafers, eachof the thin film silicon wafers being manufactured by: forming aplurality of gettering layers immediately below a device layer which isformed in a vicinity of a front surface of a semiconductor siliconwafer; fabricating a device in the device layer of the semiconductorsilicon wafer; after the device has been fabricated, capturing impurityelements within the gettering layers by performing gettering heattreatment on the semiconductor silicon wafer; and after the getteringheat treatment has been performed, removing part of the semiconductorsilicon wafer from a rear surface of the semiconductor silicon wafer toimmediately below the gettering layers together with the getting layerscontaining the impurity elements so as to leave at least one of theplurality of gettering layers in place.

A manufacturing method for a multi-layered silicon wafer according tothe present invention includes the steps of: forming a plurality ofgettering layers immediately below a device layer which is formed in avicinity of a front surface of a semiconductor silicon wafer;fabricating a device in the device layer of the semiconductor siliconwafer; after the device has been fabricated, capturing impurity elementswithin the gettering layers by performing gettering heat treatment onthe semiconductor silicon wafer; after the gettering heat treatment hasbeen performed, removing part of the semiconductor silicon wafer from arear surface of the semiconductor silicon wafer to immediately below thegettering layers together with the getting layers containing theimpurity elements so as to leave at least one of the plurality ofgettering layers in place, to thereby manufacture a thin film siliconwafer; and laminating a plurality of the thin film silicon wafers, tothereby manufacture the multi-layered silicon wafer.

Result of the Invention

As has been described above, with the thin film silicon wafer and themulti-layered silicon wafer according to the present invention, thegettering technique which is effective in both stages before and afterbeing reduced in thickness to be in a thin film form can be provided forimpurity contamination which may be a weak point of the multi-layereddevice structure in which high integration is achieved. Further, themethods according to the present invention have advantages ofefficiently manufacturing the thin film silicon wafer and themulti-layered silicon wafer of the present invention, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart illustrating an example of a step sequence for athin film silicon wafer according to the present invention.

FIG. 2 are schematic explanatory diagrams illustrating a structuralexample of the thin film silicon wafer according to the presentinvention, in which FIG. 2( a) illustrates a first structural exampleand FIG. 2( b) illustrates a second structural example.

FIG. 3 is a flow chart illustrating an example of a manufacturing stepsequence for a multi-layered silicon wafer structure according to thepresent invention.

FIG. 4 is a schematic explanatory diagram illustrating an example of astructure of the multi-layered silicon wafer structure according to thepresent invention.

FIG. 5 is a flow chart illustrating an example of a manufacturing stepsequence for a multi-layered silicon wafer according to the presentinvention.

FIG. 6 is a schematic explanatory diagram illustrating an example of astructure of the multi-layered silicon wafer according to the presentinvention.

FIG. 7 are schematic explanatory diagrams illustrating an example of amanufacturing procedure for the multi-layered silicon wafer according tothe present invention, in which FIG. 7( a) illustrates a state in whicha device layer, a first gettering layer, and a second gettering layerhave been formed on a front surface side of a semiconductor siliconwafer, FIG. 7( b) illustrates a state in which a removal part and thefirst gettering layer have been removed from a rear surface side of thesemiconductor silicon wafer in the state of FIG. 7( a), and FIG. 7( c)illustrates a state in which three thin film silicon wafers have beenbonded together.

FIG. 8 is a flow chart illustrating step sequences for two intentionalcontamination steps of Example 1, Comparative Example 1, and ComparativeExample 2 together.

FIG. 9 are schematic explanatory diagrams illustrating an example of amanufacturing procedure for a multi-layered silicon wafer sampleaccording to Comparative Example 1, in which FIG. 9( a) illustrates astate in which the device layer and the first gettering layer have beenformed on the front surface side of the semiconductor silicon wafer,FIG. 9( b) illustrates a state in which the removal part and the firstgettering layer have been removed from the rear surface side of thesemiconductor silicon wafer in the state of FIG. 9( a), and FIG. 9( c)illustrates a state in which three thin film silicon wafers have beenbonded together.

FIG. 10 are schematic explanatory diagrams illustrating an example of amanufacturing procedure for a multi-layered silicon wafer sampleaccording to Comparative Example 2, in which FIG. 10( a) illustrates astate in which the device layer has been formed on the front surfaceside of the semiconductor silicon wafer, FIG. 10( b) illustrates a statein which the removal part has been removed from the rear surface side ofthe semiconductor silicon wafer in the state of FIG. 10( a), and FIG.10( c) illustrates a state in which three thin film silicon wafers havebeen bonded together.

DESCRIPTION OF SYMBOLS

10, 10A, 10B, 10C: thin film silicon wafers, 12: a semiconductor siliconwafer, 12A, 12B, 12C: initial wafers, 14, 14A to 14F: device layers, 16,16A to 16F, 16 a, 16 b, 17: gettering layers, 18: a removal part, 20: amulti-layered silicon wafer structure, 30, 40: multi-layered siliconwafers

BEST MODE FOR CARRING OUT THE INVENTION

Hereinafter, embodiments of the present invention are described withreference to the accompanying drawings. However, those embodiments aremerely illustrative, and it should be understood that variousmodifications may made thereto without departing from the technicalconcept of the present invention.

A manufacturing method for a thin film silicon wafer according to thepresent invention includes manufacturing steps illustrated in FIG. 1.FIG. 1 is a flow chart illustrating an example of a manufacturing stepsequence for the thin film silicon wafer according to the presentinvention. First, a semiconductor silicon wafer is prepared (Step 100 ofFIG. 1). Next, one or more gettering layers are formed immediately belowa device layer which is formed in a vicinity of a front surface of thesemiconductor silicon wafer (Step 102 of FIG. 1). Subsequently, a deviceis fabricated in the device layer of the semiconductor silicon wafer(Step 104 of FIG. 1). After the device has been fabricated, part of thesemiconductor silicon wafer from a rear surface thereof to immediatelybelow the gettering layers is removed so as to leave at least one of thegettering layers in place (Step 106 of FIG. 1). Through the proceduredescribed above, a thin film silicon wafer 10 according to the presentinvention is manufactured (Step 108 of FIG. 1).

According to one aspect of the thin film silicon wafer 10, the thin filmsilicon wafer 10 has a structure in which one gettering layer 16 isprovided immediately below a device layer 14 formed in a vicinity of afront surface layer of a semiconductor silicon wafer 12, as illustratedin FIG. 2( a). In FIG. 2, reference numeral 18 denotes a removal part tobe removed from a rear surface side of the semiconductor silicon wafer12 after the gettering layer 16 has been formed. Further, according toanother aspect of the thin film silicon wafer 10, the thin film siliconwafer 10 has a structure in which a plurality of gettering layers (twolayers in the illustrated example) 16 and 17 are provided immediatelybelow the device layer 14 formed in the vicinity of the front surfacelayer of the semiconductor silicon wafer 12, as illustrated in FIG. 2(b). In the case of FIG. 2( b), the gettering layer 17 and the removalpart 18 are to be removed.

A manufacturing method for a multi-layered silicon wafer structureaccording to the present invention includes a manufacturing procedureillustrated in FIG. 3. FIG. 3 is a flow chart illustrating an example ofa manufacturing step sequence for the multi-layered silicon waferstructure according to the present invention. First, a plurality of thethin film silicon wafers 10 each having the above-mentioned structureare prepared (Step 200 of FIG. 3). Next, the plurality of the thin filmsilicon wafers are laminated (Step 202 of FIG. 3). Through the proceduredescribed above, a multi-layered silicon wafer structure 20 according tothe present invention is manufactured (Step 204 of FIG. 3).

In the multi-layered silicon wafer structure 20, as illustrated in FIG.4, each of laminated thin film silicon wafers 10A, 10B, and 10C includesan individual device, and gettering layers 16A, 16B, and 16C areprovided immediately below all of device layers 14A, 14B, and 14Cincluding the individual devices. Note that the illustrated example ofthe multi-layered silicon wafer structure 20 of FIG. 4 illustrates thecase where the three thin film silicon wafers are laminated.

A manufacturing method for a multi-layered silicon wafer according tothe present invention includes a manufacturing procedure illustrated inFIG. 5. FIG. 5 is a flow chart illustrating an example of amanufacturing step sequence for the multi-layered silicon waferaccording to the present invention. First, a semiconductor silicon waferis prepared (Step 300 of FIG. 5). Next, a plurality of gettering layersare formed immediately below a device layer which is formed in avicinity of a front surface of the semiconductor silicon wafer (Step 302of FIG. 5). Subsequently, a device is fabricated in the device layer ofthe semiconductor silicon wafer (Step 304 of FIG. 5). After the devicehas been fabricated, gettering heat treatment is performed on thesemiconductor silicon wafer, to thereby capture impurity elements withinthe gettering layers (Step 306 of FIG. 5). After the gettering heattreatment has been performed, part of the semiconductor silicon waferfrom a rear surface thereof to immediately below the gettering layers isremoved together with the getting layers containing the impurityelements so as to leave at least one of the plurality of getteringlayers in place (Step 308 of FIG. 5). Through the procedure describedabove, a thin film silicon wafer is manufactured (Step 310 of FIG. 5). Aplurality of the thin film silicon wafers are laminated (Step 312 ofFIG. 5). Through the laminating process, a multi-layered silicon wafer30 according to the present invention is completed (Step 314 of FIG. 5).

In the multi-layered silicon wafer 30, as illustrated in FIG. 6, each oflaminated layers 10D, 10E, and 10F includes an individual device, andgettering layers 16D, 16E, and 16F which have captured the impurityelements are provided immediately below all of device layers 14D, 14E,and 14F including the individual devices. Note that the illustratedexample of the multi-layered silicon wafer 30 of FIG. 6 illustrates thecase where the three thin film silicon wafers are laminated.

Hereinafter, the manufacturing procedure for the multi-layered siliconwafer according to the present invention is described more specifically.FIG. 7 are schematic explanatory diagrams illustrating an example of themanufacturing procedure for the multi-layered silicon wafer according tothe present invention. FIG. 7( a) illustrates a state in which a devicelayer, a first gettering layer, and a second gettering layer have beenformed on a front surface side of a semiconductor silicon wafer, FIG. 7(b) illustrates a state in which a removal part and the first getteringlayer have been removed from a rear surface side of the semiconductorsilicon wafer in the state of FIG. 7( a), and FIG. 7( c) illustrates astate in which three thin film silicon wafers have been bonded together.In this example, as illustrated in FIG. 7( a), the two gettering layers16 a and 16 b are provided when each of the thin film silicon wafers 10is manufactured. Such a technique capable of performing gettering over arelatively wider area is used for the first gettering layer 16 a as tobe a high concentration boron layer (p⁺ layer) or a layer having highBMD density (IG layer: Internal Gettering layer). The second getteringlayer 16 b is an ion-implantation layer, and as to the second getteringlayer 16 b, on the assumption that the device layer 14 is normallyformed in the vicinity of the front surface layer of the semiconductorsilicon wafer 12, there is used a technique capable of forming agettering layer over a relatively narrower area so as to be formed at adepth position of several m from the front surface layer.

As described above, the first gettering layer 16 a and the secondgettering layer 16 b are formed on the front surface side of thesemiconductor silicon wafer (FIG. 7( a)). For convenience of descriptionin Example 1, the silicon wafer in this state is referred to as aninitial wafer 12A. Next, after a device has been fabricated in thedevice layer 14, the first gettering layer 16 a and the removal part 18are removed (FIG. 7( b)). A plurality of the thin film silicon wafers 10thus manufactured (three in the illustrated example) are bondedtogether, to thereby complete a multi-layered silicon wafer 40 accordingto the present invention (FIG. 7( c)).

EXAMPLES

Hereinafter, while description will be given of the present invention inmore concrete manner taking up examples below, it is needless to saythat the examples are shown by way of illustration only and should notbe construed by way of limitation.

Example 1

The multi-layered silicon wafer having the structure illustrated in FIG.7( c) was manufactured. Note that, in this example, the first getteringlayer is a high concentration boron layer while the second getteringlayer is a layer formed by performing ion-implantation of B at 2 MeV andwith a dose of 10¹⁵ cm⁻². Gettering capability evaluation was performedon this wafer through intentional contamination.

In this example, in a lamination bonding step for the thin film siliconwafers, two situations were prepared for an intentional contaminationstep. FIG. 8 is a flow chart illustrating step sequences for the twointentional contamination steps together. In the first case ofintentional contamination, first, the initial wafer 12A (in the state inwhich the first gettering layer and the second gettering layer wereformed on the semiconductor silicon wafer but the first gettering layerhad not yet been removed, that is, in the state of FIG. 7( a)) wasprepared (Step 400 of FIG. 8). The initial wafer 12A was intentionallycontaminated with Cu at a concentration of 4×10¹² cm⁻³ (Step 401 of FIG.8), and the first gettering layer 16 a was removed (Step 402 of FIG. 8).A plurality of the thin film silicon wafers in this state (three in thisexample) were laminated and deposited, and heat treatment was performedthereon for one hour at 400° C. (Step 404 of FIG. 8). Thereafter, a Cuconcentration in the vicinity of the front surface layer was evaluatedby a chemical analysis method, to thereby perform gettering capabilityevaluation (Step 406 of FIG. 8).

In contrast to this, the second case of intentional contamination isdifferent from the first case of intentional contamination in that theinitial wafer 12A was not intentionally contaminated and that the thinfilm silicon wafer being a thinned layer after the first gettering layerhad been ground to be removed (in the state of FIG. 7( b)) wasintentionally contaminated with Cu at a concentration of 4×10¹² cm⁻³(Step 403 of FIG. 8). However, the remaining procedure is identical withthe first case of intentional contamination, and hence repetitivedescription is omitted.

Comparative Example 1

In this comparative example, there was used a sample in which only thefirst gettering layer was formed while no second gettering layer wasformed in the manufacturing example of Example 1 illustrated in FIG. 7.A manufacturing procedure for the sample is illustrated in FIG. 9. FIG.9 are schematic explanatory diagrams illustrating an example of themanufacturing procedure for the multi-layered silicon wafer sampleaccording to Comparative Example 1. FIG. 9( a) illustrates a state inwhich the device layer and the first gettering layer have been formed onthe front surface side of the semiconductor silicon wafer, FIG. 9( b)illustrates a state in which the removal part and the first getteringlayer have been removed from the rear surface side of the semiconductorsilicon wafer in the state of FIG. 9( a), and FIG. 9( c) illustrates astate in which three thin film silicon wafers have been bonded together.

As described above, in manufacturing the sample of Comparative Example 1of FIG. 9, only the first gettering layer 16 a is formed on the frontsurface side of the semiconductor silicon wafer 12 to form an initialwafer 12B (FIG. 9( a)), and after a device has been fabricated in thedevice layer 14, the first gettering layer 16 a and the removal part 18are removed (FIG. 9( b)). A plurality of thin film silicon wafers 11thus manufactured (three in the illustrated example) were laminated tobe bonded together, to thereby manufacture a multi-layered silicon wafer50 according to Comparative Example 1 (FIG. 9( c)). Gettering capabilityevaluation was performed on this wafer through intentional contaminationsimilarly to Example 1. Note that the initial wafer 12B was used as theinitial wafer of the flow chart of FIG. 8.

Comparative Example 2

In this comparative example, there was used a sample in which neitherthe first gettering layer nor the second gettering layer was formed inthe manufacturing example of Example 1 illustrated in FIG. 7. Amanufacturing procedure for the sample is illustrated in FIG. 10. FIG.10 are schematic explanatory diagrams illustrating an example of themanufacturing procedure for the multi-layered silicon wafer sampleaccording to Comparative Example 2. FIG. 10( a) illustrates a state inwhich the device layer has been formed on the front surface side of thesemiconductor silicon wafer, FIG. 10( b) illustrates a state in whichthe removal part has been removed from the rear surface side of thesemiconductor silicon wafer in the state of FIG. 10( a), and FIG. 10( c)illustrates a state in which three thin film silicon wafers have beenbonded together.

As described above, in manufacturing the sample of Comparative Example 2of FIG. 10, no gettering layer is formed on the front surface side ofthe semiconductor silicon wafer, and the wafer in this state is referredto as an initial wafer 12C (FIG. 10( a)). Next, after a device has beenfabricated in the device layer 14, the removal part 18 is removed (FIG.10( b)). A plurality of thin film silicon wafers 13 thus manufactured(three in the illustrated example) are laminated to be bonded together,to thereby manufacture a multi-layered silicon wafer 60 according toComparative Example 2 (FIG. 10( c)). Gettering capability evaluation wasperformed on this wafer through intentional contamination similarly toExample 1. Note that the initial wafer 12C was used as the initial waferof the flow chart of FIG. 8. Further, because the initial wafer 12Cincludes no first gettering layer, it is the removal part 18 that isremoved in a process corresponding to that of Step 402 of FIG. 8.

Results of the gettering capability evaluation according to Example 1,Comparative Example 1, and Comparative Example 2 are illustrated inTable 1. As to Example 1, it is found that the Cu concentrations in thevicinity of the front surface layer are equal to or lower than adetection lower limit value, irrespective of the situations in which thecontamination steps have been performed, and that the getteringeffectively worked against contamination by Cu at any stage of themulti-layered wafer formation process. In contrast to this, as toComparative Example 1, the gettering does not work at all against thecontamination in the second contamination step, that is, after the firstgettering layer has been peeled off, which results in detection of Cu inthe vicinity of the front surface layer. As to Comparative Example 2,because the wafer including no gettering layer is used in all steps, thegettering does not work, which makes high the Cu concentrations in thevicinity of the front surface layer not depending on the situations ofthe contamination steps.

TABLE 1 Cu concentration in vicinity of front surface layer (cm⁻³)Contamination before Contamination after removal of first removal offirst gettering layer gettering layer (first case) (second case) ExampleD.L. D.L. Comparative Example 1 D.L. 4 × 10¹²(cm⁻³) (only with p⁺ layerof first layer) Comparative Example 2 4 × 10¹²(cm⁻³) 4 × 10¹²(cm⁻³)(with no gettering layer) Initial contamination concentration = 4 × 10¹²(cm⁻³) D.L.: detection lower limit value or less

It is understood from the above that the multi-layered silicon waferdescribed in Example 1 of the present invention has strong getteringcapability.

Note that the present invention is not limited to the embodimentsdescribed above. The embodiments described above are merely illustrativeand all such equivalences that have substantially the same structure asthe technical concept described in CLAIMS of the present invention so asto provide the similar actions and effects are encompassed in thetechnical scope of the present invention.

For example, in Examples described above, the high concentration boronsubstrate is used as the first gettering layer, but the first getteringlayer may be an IG wafer having high BMD density. Also, the boron isused as the ion-implantation seed for the second gettering layer, butother elements fall under the category of the present invention as longas the similar capability can be exhibited. Further, the secondgettering layer is not limited to the ion-implantation layer, and an RTAmethod and heat treatment can be also effectively employed as long as ahigh BMD density layer can be formed at the depth position of the secondgettering layer.

The invention claimed is:
 1. A manufacturing method for a thin filmsilicon wafer which has gettering capability even after having beenreduced in thickness to be in a thin film form and includes a devicelayer having a front device layer surface and a rear device layersurface disposed opposite the front device layer surface, themanufacturing method comprising the steps of: forming a first getteringlayer on the rear device layer surface, the first gettering layer beingfabricated from a first gettering material; forming a second getteringlayer on the first gettering layer, the second gettering layer beingfabricated from a second gettering material being different from thefirst gettering material thereby forming a unitary structure having thefirst gettering layer sandwiched between and in facial contact with therear device layer surface and the second gettering layer; fabricating adevice on the front device layer surface of the device layer; and afterthe device has been fabricated, removing the second gettering layer soas to leave the first gettering layer in place and in facial contactwith the rear device layer surface of the device layer.
 2. Amanufacturing method according to claim 1, wherein one of the first andsecond gettering layers is fabricated from either a high concentrationp⁺ boron material or a material having a high density of bulk microdefects and a remaining one of the first and second gettering layers isfabricated from an ion-implantation material.
 3. A manufacturing methodfor a multi-layered silicon wafer including a device layer having afront device layer surface and a rear device layer surface disposedopposite the front device layer surface, the manufacturing methodcomprising the steps of: forming a first gettering layer on the reardevice layer surface, the first gettering layer being fabricated from afirst gettering material; forming a second gettering layer on the firstgettering layer, the second gettering layer being fabricated from asecond gettering material being different from the first getteringmaterial thereby forming a unitary structure having the first getteringlayer sandwiched between and in facial contact with the rear devicelayer surface and the second gettering layer; fabricating a device onthe front device layer surface of theof the device layer; after thedevice has been fabricated, capturing impurity elements within the firstand second gettering layers by performing gettering heat treatment;after the gettering heat treatment has been performed, removing thesecond gettering layer so as to leave the first gettering layer in placeand in facial contact with the rear device layer surface of the devicelayer; and laminating a plurality of the thin film silicon wafers, tothereby manufacture the multi-layered silicon wafer.
 4. A manufacturingmethod according to claim 3, wherein one of the first and secondgettering layers is fabricated from either a high concentration p⁺ boronmaterial or a material having a high density of bulk micro defects and aremaining one of the first and second gettering layers is fabricatedfrom an ion-implantation material.